Enhanced status code

SMTP error X.1.9

Relayed to non-compliant mailer

Updated Jul 1, 2026

The short answer

Relayed to non-compliant mailer Common cause: Message was forwarded to a system that cannot report more detail

Quick fix

Check the downstream relay or destination system

This code is written X.1.9 because the reason is the same whether the failure is temporary (a 4 first digit) or permanent (a 5). Read the first digit of your own bounce to know which applies.

How to fix it

Check the downstream relay or destination system

Related codes

X.1.0 Other address status X.1.1 Bad destination mailbox address X.1.2 Bad destination system address X.1.3 Bad destination mailbox address syntax X.1.4 Destination mailbox address ambiguous X.1.5 Destination address valid
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